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Taxonomy

The Adélie Penguin is one of three species in the genus Pygoscelis. Mitochondrial and nuclearDNA evidence suggests the genus split from other penguins around 38 million years ago, about 2 million years after the ancestors of the genus Aptenodytes. In turn, the Adélie penguins split off from the other members of the genus around 19 million years ago.[2]

Distribution and habitat

There are 38 colonies of Adélie penguins, and there are over 5 million Adélies in the Ross Sea region. Ross Island supports a colony of approximately half a million Adélies. The Adélie penguins breed from October to February on shores around the Antarctic continent. Adélies build rough nests of stones. Two eggs are laid, these are incubated for 32 to 34 days by the parents taking turns (shifts typically last for 12 days). The chicks remain in the nest for 22 days before joining crèches. The chicks moult into their juvenile plumage and go out to sea after 50 to 60 days. Adélie penguins live in groups called colonies.

Description

These penguins are mid-sized, being 46 to 75 cm (18 to 30 in) in length and 3.6 to 6 kg (7.9 to 13 lb) in weight.[3][4] Distinctive marks are the white ring surrounding the eye and the feathers at the base of the bill. These long feathers hide most of the red bill. The tail is a little longer than other penguins' tails. The appearance looks somewhat like a tuxedo. They are a little smaller than other penguin species. Their appearance is closest to the stereotypical image of penguins as mostly black with a white belly.

Adélie penguins can swim up to 45 miles per hour (72 km/h).[citation needed]

Behaviour

Like all penguins, the Adélie is highly social, foraging and nesting in groups. They are also very aggressive to other penguins that steal stones from their nest.

Specifics of their behaviour were documented extensively by Apsley Cherry-Garrard (a survivor of Robert Falcon Scott’s fateful final journey to the South Pole) in his book The Worst Journey in the World. Cherry-Garrard noted: “They are extraordinarily like children, these little people of the Antarctic world, either like children or like old men, full of their own importance."[5] Certain displays of their selfishness were commented upon by George Murray Levick, a Royal Navy Surgeon-Lieutenant and scientist who also accompanied Scott on his ill-fated British Antarctic Expedition 1910, during his surveying of penguins in the Antarctic: "At the place where they most often went in [the water], a long terrace of ice about six feet in height ran for some hundreds of yards along the edge of the water, and here, just as on the sea-ice, crowds would stand near the brink. When they had succeeded in pushing one of their number over, all would crane their necks over the edge, and when they saw the pioneer safe in the water, the rest followed.”[6]

It was observed how the penguin's intrigue could also put them in harm’s way, which Scott found a particular nuisance:

“The great trouble with [the dog teams] has been due to the fatuous conduct of the penguins. Groups of these have been constantly leaping on to our [ice] floe. From the moment of landing on their feet their whole attitude expressed devouring curiosity and a pig-headed disregard for their own safety. They waddle forward, poking their heads to and fro in their usually absurd way, in spite of a string of howling dogs straining to get at them. “Hulloa!” they seem to say, “here’s a game – what do all you ridiculous things want?” And they come a few steps nearer. The dogs make a rush as far as their harness or leashes allow. The penguins are not daunted in the least, but their ruffs go up and they squawk with semblance of anger.”[7]

Regularly this attitude lead to the demise of an Adélie penguin, "Then the final fatal steps forward are taken and they come within reach. There is a spring, a squawk, a horrid red patch on the snow, and the incident is closed.”[7] Others on the mission to the South Pole were more receptive of this element of the Adélies' intrigue. Cherry-Garrard:

“Meares and Dimitri exercised the dog-teams out upon the larger floes when we were held up for any length of time. One day a team was tethered by the side of the ship, and a penguin sighted them and hurried from afar off. The dogs became frantic with excitement as he neared them: he supposed it was a greeting, and the louder they barked and the more they strained at their ropes, the faster he bustled to meet them. He was extremely angry with a man who went and saved him from a very sudden end, clinging to his trousers with his beak, and furiously beating his shins with his flippers.”[8]

This was an occurrence of some regularity, “It was not an uncommon sight to see a little Adélie penguin standing within a few inches of the nose of a dog which was almost frantic with desire and passion.”[8]

Due to their obstinate personality traits Cherry-Garrard held the birds in great regard, “Whatever [an Adélie] penguin does has individuality, and he lays bare his whole life for all to see. He cannot fly away. And because he is quaint in all that he does, but still more because he is fighting against bigger odds than any other bird, and fighting always with the most gallant pluck.”[9]

Diet

The Adélie penguin is known to feed mainly on Antarctic krill, ice krill, Antarctic silverfish, and Glacial Squid (diet varies depending on geographic location) during the chick-rearing season. The stable isotope record of fossil eggshell accumulated in colonies over the last 38,000 years reveals a sudden change from a fish-based diet to krill that started two hundred years ago. This is most likely due to the decline of the Antarctic Fur Seal since the late 18th century and Baleen whales in the 20th century. The reduction of competition from these predators has resulted in a surplus of krill, which the penguins now exploit as an easier source of food.[10]

Reproduction

Adélie penguins arrive at their breeding grounds in October or November, at the end of winter and the start of spring. Their nests consist of stones piled together. In December, the warmest month in Antarctica (about −2 °C or 28 °F), the parents take turns incubating the egg; one goes to feed and the other stays to warm the egg. The parent who is incubating does not eat. In March, the adults and their young return to the sea. The Adélie penguin lives on sea ice but needs the ice-free land to breed. With a reduction in sea ice and a scarcity of food, populations of the Adélie penguin have dropped by 65% over the past 25 years.[11]

Young Adélie penguins who have no experience in social interaction may react to false cues when the penguins gather to breed. They may, for instance, attempt to mate with other males, with young chicks or with dead females. On account of the birds' relatively human-like appearance and behavior, human observers have interpreted this behavior anthropomorphically as sexual deviance. The first to record such behavior was Dr. Levick, in 1911 and 1912, but his notes were deemed too indecent for publication at the time; they were rediscovered and published in 2012. "The pamphlet, declined for publication with the official Scott expedition reports, commented on the frequency of sexual activity, auto-erotic behaviour, and seemingly aberrant behaviour of young unpaired males and females, including necrophilia, sexual coercion, sexual and physical abuse of chicks and homosexual behaviour," states the analysis written by Douglas Russell and colleagues William Sladen and David Ainley. "His observations were, however, accurate, valid and, with the benefit of hindsight, deserving of publication."[12][13] Levick observed the Adélie penguins at Cape Adare, the site of the largest Adelie penguinrookery in the world.[14] As of June 2012[update], he has been the only one to study this particular colony and he observed it for an entire breeding cycle.[15] The discovery significantly illuminates the behaviour of the species that some researchers[16] believe to be an indicator of climate change.[15]

Migration

Adélie penguins living in the Ross Sea region in Antarctica and migrate an average of about 13,000 kilometres (8,100 mi) during the year as they follow the sun from their breeding colonies to winter foraging grounds and back again. The longest treks have been recorded at 17,600 kilometres (10,900 mi).[17]